Leigh Brasington has lots of links on his jhaana page that I found independently before I found his website. I won't paste the links we have in common on this post. http://www.leighb.com/jhanas.
Ven. Maháthera Henepola Gunaratana's book on jhaanas (PhD thesis), other books and online videos of interviews with him are interesting and very useful. The jhaana book is online and linked fromLeigh Brasington's website. Ven. Maháthera Henepola Gunaratana is featured on DhammaTube videos on YouTube and Veoh.com. There are also many excellent Dhamma resources produced by the Ven. Maháthera on the Bhavana Society website.
Ven. Pa Auk Sayadaw: Ven. Pa Auk Sayadaw's websites and his books in English translation are also linked from Leigh Brasington's website. http://www.paauk.org/index.
Without practice and seeing for myself, I have so far relied on textual sources. Ven. Pa Auk's teaching as described in books and by his followers is quite consistent with the Paali Canon. The only part of Ven. Pa Auk Sayadaw's teaching I don't understand is kalaapa. I have not found kalaapa in the Sutta and only found the word as a minor reference in the Visuddhimagga. The Concise Pali-English Dictionary by Ven. A.P.Buddhadatta Mahaathera defines Kalaapa as 1. a bundle; sheaf; 2. a quiver; 3. a group of elementary particles. Childers refers to it in conjunctions of string of pearls and a peacock's tail feathers. The definition of a "group of elementary particles" comes closest to the meaning used by Ven. Pa Auk Sayadaw. Perhaps the term is significant in Abhidhamma texts. I haven't yet found any references on the Internet for articles that refer to this use of Kalaapa by Ven. Pa Auk Sayadaw. [UPDATE]
Ven. Pa Auk Sayadaw suggests that once yogis have completed the jhaana training up to the eight jhaana (four ruupa jhaana and four aruupa jhaana) and attained the five jhaana mastery's, they will begin four element vipassana practice and see the kalaapa as individual glowing particles or as bundles of them. The yogi will see these kalaapa are the fundamental particles of ultimate reality that lie beneath apparent reality [look out, I've paraphrased].
Maybe I need to attain full mastery of all eight jhaana and then I'll understand. The concept also seems like a simsapa leaf from another tree. It may be true, it may exist, but is it useful or essential to the path of liberation? Perhaps yogis that can see kalaapa may truely see the emptiness of self, the lack of substance in body and mind. Then detachment, dispassion and liberation follow.
Tina Rasmussen and Stephen Snyder manage the JhaanasAdvice.com website, teach and train. I ordered their book "Jhanas Advice from Two Spiritual Friends: Concentration Meditation as Taught by Ven. Pa Auk Sayadaw" and a CD ROM with MP3 talks. Their talks maybe downloaded from their website too. The book appears aimed toward yogis who may be relatively new to jhaana practice. They refer sometimes to yogis who may be trying jhaana practice after some experience (months or years...) with Mahasi vipassana or Goenka vipassana techniques.
I sense they are very sincere and respect them for their efforts to teach meditation and spread Ven. Pa Auk Sayadaw's system of meditation to a wider range of yogis. They are very gentle and not in the least bit critical of other meditation techniques. They also refer to kalaapa...
I also recommend Ven. Buddhadhasa Bhikkhu's book "Anapanasati" which has been translated from Thai for two quite different English editions. Ven. Buddhadasa's book is a commentary on the Aanaapanasati Sutta - Mindfulness of Breathing.
1. translated from the Thai by Ven. Santikaro Bhikkhu http://www.what-buddha-taught.
2. translated from the Thai by Ven. Bhikkhu Nagasena http://www.buddhanet.net/pdf_
I prefer Ven. Bhikkhu Nagasena's translation which is more detailed than Ven. Santikaro Bhikkhu's version. It seems closer to the original Thai volume which I bought in 1984 and gave away to a friend earlier this year. Ven. Santikaro Bhikkhu refers to the tapes and may not have used tapes rather than the published Thai book. They are both good though.
The Visuddhimagga is the core text for describing various samatha and vipassana meditation techniques taught by contemporary teachers including Ven. Pa Auk Sayadaw. I visited the Mahasi Centre in Yangon in January 2007, where I saw all the inside walls of the Mahasi Sayadaw Mausoleum beautifully decorated with Ven. Mahasi Sayadaw's Burmese language translation of the Visuddhimagga. Ven. Mahasi Sayadaw cited the Visuddhimagga as support for the vipassana meditation technique he promoted.
Ven. Ajahn Brahmavamso (Ajahn Brahm) based in Perth has written and spoken a lot about jhaana. I have a recent published book of his called "Mindfulness, Bliss, and Beyond: A Mediator's Handbook" which describes the technique for attaining jhaanas. The book has a tentative forward by Jack Kornfield. I haven't practiced jhaana yet so I can't comment with authority of experience. However, I note that some of Ven. Ajahn Brahm's assertions about the nature of jhaana and requirements for attainment of ariyamagga and phala are not consistent with Ven. Mahasi Sayadaw tradition or even other Samatha traditions. For example, Leigh Brasington's description of jhaanas differ markedly.
In describing a lay follower's experience, Ven. Ajahn Brahm writes (p. 154) "Another strange quality that distinguishes jhaana from all other experiences is that within jhaana, all the senses are totally shut down. One cannot see, hear, smell, taste or feel touch. One cannot hear a crow cawing [magpies caw a lot at his centre near Perth Western Australia] or a person coughing... no heart beat registered on the ECG, and no brain activity was seen by the EEG." The lay follower had been meditating at home and gone into first jhaana for the first time. His wife found him and couldn't wake him or feel a pulse so she called an ambulance...
Ven. Ajahn Brahm also writes (p. 225) "A recurring topic among our Sangha is, can one attain to stream winning without any experience of jhaana? As should be obvious from what has been written so far, I cannot see a possibility of penetrating to the fully meaning of anattaa, dukkha and anicca without the radical data gained in jhaana experience. Yet, there are some stories in the Tipitaka ... that suggest that it might be possible." He then refers to the story of 31 soldiers of King Ajaatasattu sent by Ven. Devadatta to kill the Lord Buddha. Lord Buddha interrupts them, teaches them Dhamma and they all became Sotapannas just by listening to the Dhamma. These are soldiers who live a rough life, probably never kept even five precepts and yet they attained Sotapanna. Ven. Ajahn Brahm over looks many other examples in the Suttas including Ven. Sariputta and Ven. Moggallana who both attained Sotapanna by listening to Dhamma (Vinaaya 1:39). Ven. Sariputta attained Arahat by listening to the Dhamma (he was fanning the Lord Buddha at the same time) in the Dighanaka Sutta (MN 74). Ven. Ajahn Brahm writes that in our cynical modern world it would be impossible for someone to have enough confidence and energy to attain Sotapanna without jhaana. This is the difference between saddhaanusaarii and dhammaanusaarii (faith follower and a dhamma follower).
Many of Ven. Ajahn Brahm's video, audio and text discourses are available for download from the following website: http://www.bswa.org.au/
Ven. Dhammavuddho writes that attaining up to Sakidagaami is possible without jhaana but further attainments to Anaagaami and Arahat are only possible with jhaana. In an article "Liberation: Relevance of Sutta-Vinaya"on the following website, you can go to page 12 for the Sutta references. http://www.vbgnet.org/
Ven. Dhammavuddho was a Mahayana monk in Malaysia described in a video available from YouTube/DhammaTube and Veoh.com how he was forcibly disrobed on orders from his master because he had published many books indicating the contradictions and problems in Mahayana Buddhism. He then went to Thailand and ordained as a Theravada monk and then went to Wat Pananachaht for training. Now he is an Abbot of Vihara Buddha Gotama in Malaysia. He is a meditator and scholar. The VBG website has many photos of the centre and many excellent Dhamma articles in English, Chinese and Bahasa.